CN118268368A - High-alloy hot-working die steel bar and rolling method thereof - Google Patents
High-alloy hot-working die steel bar and rolling method thereof Download PDFInfo
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- 238000005096 rolling process Methods 0.000 title claims abstract description 161
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- 238000000034 method Methods 0.000 title claims abstract description 39
- 238000001816 cooling Methods 0.000 claims abstract description 42
- 238000004513 sizing Methods 0.000 claims abstract description 39
- 239000013072 incoming material Substances 0.000 claims abstract description 18
- 238000001514 detection method Methods 0.000 claims abstract description 13
- 238000010583 slow cooling Methods 0.000 claims abstract description 10
- 238000004321 preservation Methods 0.000 claims description 21
- 238000002791 soaking Methods 0.000 claims description 10
- 238000010438 heat treatment Methods 0.000 abstract description 16
- 230000007547 defect Effects 0.000 abstract description 12
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- 229910000851 Alloy steel Inorganic materials 0.000 description 2
- 229910000734 martensite Inorganic materials 0.000 description 2
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Abstract
The invention belongs to the technical field of metal material deformation heat treatment, and relates to a high-alloy hot working die steel bar material and a rolling method thereof. The rolling method comprises the steps of sequentially heating a steel billet of hot-working die steel, rough rolling, first heat-preserving cooling, middle rolling, second heat-preserving cooling, three-roller reducing sizing finish rolling, third heat-preserving cooling, sawing, collecting, bundling, pit-entering slow cooling and pit-exiting to obtain a hot-working die steel bar; the total alloy element content of the hot work die steel is more than 8 percent by weight, and the diameter specification of the finished product is phi 30-phi 70; the total pass of the rough rolling and the middle rolling is 12-16 times; and the three-roller reducing sizing finish rolling is carried out, the diameter specification of the reducing sizing incoming material is phi 40-phi 75, and the finish rolling passes are 4-5 times. According to the invention, through designing a heating rolling process of three-roller reducing sizing finish rolling of the medium-small-specification high alloy bar, free rolling with any specification of phi 30-phi 70 can be realized, the production cost is reduced, and the quality of the high alloy bar is promoted. The tolerance size of the rolled high alloy bar meets 0 to +0.5mm, the out-of-roundness is less than or equal to 0.35mm, the defects of surface folding, lugs, stress cracking and the like are avoided, and the flaw detection quality meets the GB/T4162-2022 standard A-level requirement.
Description
Technical Field
The invention belongs to the technical field of metal material deformation heat treatment, and relates to a high-alloy hot working die steel bar material and a rolling method thereof.
Background
The die is a basic tool for industrial production, hot work die steel is an important part of die steel, and the service environment is more and more severe along with the development of industry. The 4Cr5MoSiV1 hot work die steel is air quenched martensitic high strength steel, and is widely applied to the manufacture of dies such as hot extrusion and hot forging at present.
At present, the 4Cr5MoSiV1 bar is mainly forged or rolled into a material, and the material is forged into a large specification (generally more than phi 70) to ensure the production efficiency; the medium and small specification (generally less than or equal to phi 70) adopts rolling stock, wherein the rolling is mainly performed by a two-roller mill. When the two-roller rolling is adopted for forming the product, the defects of unstable tolerance, lugs, folding and the like are easily caused when the 4Cr5MoSiV1 alloy is rolled by the two rollers, the rolled product is directly scrapped when the rolling condition is serious, and the dimensional tolerance can only meet the 3 groups of tolerance level of national standard GB/T702-2017 (the tolerance of more than 30 and 50 is +/-0.6 mm, the out-of-roundness is less than or equal to 0.6mm, the tolerance of more than 50 and 70 is +/-0.8 mm, and the out-of-roundness is less than or equal to 1.04 mm) when the rolling condition is good. Therefore, a part processing factory often needs to enlarge the specification order, and the bar is turned and then subjected to the subsequent finish machining process, so that the cost and the resource waste are caused; and when two rolls are rolled, one pair of pass can only roll one specification, the rolling efficiency is extremely low for small batches and multiple specifications, and the rolling cost of a steel mill is increased.
In order to reduce the processing cost and the processing flow, some die processing factories meet the requirement that the tolerance size of 4Cr5MoSiV1 alloy bars with the specification of phi 30-phi 70 is 0 to +0.5mm, the out-of-roundness is less than or equal to 0.35mm, and the required tolerance size is far higher than the 3 groups of level of national standard GB/T702-2017, and the delivery requirement cannot be met by adopting conventional two-roll rolling.
The three-roller reducing sizing mill has unique characteristics and production convenience (the three-roller reducing sizing mill is shown in a schematic diagram in fig. 1), and compared with a two-roller mill, the three-roller reducing sizing mill has the greatest advantages that functions of single pass rolling, free size rolling, high-precision rolling, high-efficiency production, on-line quick roll changing, remote size adjustment and the like can be realized, the production operation rate can be effectively improved, and 3-6 mm group spacing specification adjustment can be completed in 1min only through on-line remote adjustment. Three-roll reducing mills (e.g., KOCKS mill) have become increasingly popular in China, but are currently mainly used for producing low alloy steels of less than or equal to 5% wt, and are rarely reported in the field of high alloy rolling production of more than 8% wt.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide the high alloy hot working die steel bar and the rolling method thereof, and the heating rolling process of three-roller reducing sizing finish rolling of the medium-small specification high alloy bar is designed, so that the dimensional accuracy of the high alloy hot working die steel can be improved, free rolling with any specification phi 30-phi 70 can be realized, the production cost is reduced, and the quality of the high alloy bar is promoted. The tolerance size of the rolled high alloy bar meets 0 to +0.5mm, the out-of-roundness is less than or equal to 0.35mm, the defects of surface folding, lugs, stress cracking and the like are avoided, and the flaw detection quality meets the GB/T4162-2022 standard A-level requirement.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
According to the rolling method of the high-alloy hot-work die steel bar, a billet of the hot-work die steel is sequentially heated, rough rolled, first heat-preserving and cooling, middle rolled, second heat-preserving and cooling, three-roller reducing and sizing finish rolling, third heat-preserving and cooling, sawing, collecting, bundling, pit-entering slow cooling and pit-leaving to obtain the hot-work die steel bar;
the total alloy element content of the hot work die steel is more than 8 percent by weight, and the diameter specification of the finished product is phi 30-phi 70;
The total pass of the rough rolling and the middle rolling is 12-16 times;
And the three-roller reducing sizing finish rolling is carried out, the diameter specification of the reducing sizing incoming material is phi 40-phi 75, and the finish rolling passes are 4-5 times.
Further, the brand of the hot work die steel is 4Cr5MoSiV1;
and/or when the diameter specification of the finished product is phi 30-phi 36 and phi 36-phi 41 respectively, the total pass of rough rolling and middle rolling is 16 times, and the diameter specification of the reduced sizing incoming material is phi 40 and phi 46 respectively;
And/or when the diameter specifications of the finished product are phi 41-phi 48 and phi 48-phi 57 respectively, the total pass of rough rolling and middle rolling is 14 times, and the diameter specifications of the reduced sizing incoming material are phi 52 and phi 61 respectively;
And/or when the diameter specifications of the finished product are phi 57-phi 64 and phi 64-phi 70 respectively, the total pass of rough rolling and middle rolling is 12 times, and the diameter specifications of the reduced sizing incoming material are phi 68 and phi 75 respectively;
and/or, the rough rolling passes are 6 passes;
and/or, the finish rolling passes are 4 times.
Further, the heated preheating section temperature: 550-650 ℃, soaking section temperature: 1170-1230 ℃, soaking and preserving heat for 60-120 min.
Further, the initial rolling temperature of the rough rolling: 1070-1130 ℃;
And/or, the rough rolling is preceded by adopting high-pressure air to remove scales.
Further, the finishing temperature of the three-roll reducing and sizing finish rolling: and is more than or equal to 920 ℃.
Further, the first heat preservation cooling and the second heat preservation cooling are both carried out on a roller way provided with a heat preservation cover; the third heat preservation and cooling are carried out on a cooling bed with a heat preservation cover.
Further, the temperature of the cooling bed on the steel billet is as follows: the temperature of the cooling bed heat preservation cover is not less than 880 ℃: 550-650 ℃.
Further, the pit entering slow cooling temperature is as follows: not less than 350 ℃; the pit outlet temperature is as follows: the temperature is less than or equal to 100 ℃.
In a second aspect, a high alloy hot work die steel bar is obtained by the rolling method.
Further, the high alloy hot work die steel bar is a 4Cr5MoSiV1 bar, the diameter specification is phi 30-phi 70, the detection tolerance size is 0- +0.5mm according to GB/T702-2017, and the out-of-roundness is less than or equal to 0.35mm; the ultrasonic flaw detection quality meets the A-level requirement of GB/T4162-2022 standard.
The invention designs a heating and rolling process for finish rolling of the three-roller reducing sizing mill by analyzing the high alloy characteristics of hot work die steel, and has at least the following beneficial effects compared with the prior art:
(1) The rolling method has reasonable design of heating and rolling processes, designs forming passes with different forming specification ranges and reducing sizing incoming material specifications, realizes that a three-roller reducing sizing mill finish rolling finished product replaces a conventional two-roller mill finished product, and improves the rolling dimensional accuracy of the high alloy hot working die steel bar.
(2) According to the invention, the heating temperature, the rolling temperature and the cooling after rolling are controlled, and three-roller reducing sizing rolling is adopted to finish rolling the finished product, so that the alloy bar with good tolerance size and core quality is obtained. The technology can accurately control the temperature conditions of key points so as to obtain the required round bar, and has the characteristic of high controllable degree.
(3) The high alloy bar rolled by adopting the process provided by the invention has the specification range phi 30-phi 70, the roll replacement is not needed in the same group of distance specifications, free rolling can be realized by any specification to meet the individual requirements of customers on the steel size, and the process tool is simple to prepare and high in production efficiency. The tolerance size after rolling is +0.1- +0.4mm, the out-of-roundness is 0.15-0.25 mm, the defects of surface folding, lugs, stress cracks and the like are avoided, the flaw detection quality meets the GB/T4162-2022 standard A-level requirement, and the rolling size precision is far higher than that of the conventional rolling technology.
Drawings
FIG. 1 is a schematic view of a three roll reducing sizing pass.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described in the following in conjunction with the embodiments of the present invention. The embodiments of the present invention are implemented on the premise of the technical solution of the present invention, and detailed embodiments and processes are given, but the scope of the present invention is not limited to the following embodiments, which should be understood by those skilled in the art to help understand the present invention, and should not be construed as being a specific limitation of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The endpoints of the ranges and any values disclosed in the present invention are not limited to the precise range or value, and the range or value should be understood to include values close to the range or value. For numerical ranges, one or more new numerical ranges may be obtained in combination with each other between the endpoints of each range, between the endpoint of each range and the individual point value, and between the individual point values, and are to be considered as specifically disclosed in the present invention.
In the present invention, unless specified and/or indicated otherwise, all numbers referring to amounts of components are "weight or weight ratio" throughout. The process parameters for the specific conditions not noted in the examples below are generally as usual. The starting materials described in the examples below are all commercially available from the public.
A rolling method of high alloy hot work die steel bar sequentially comprises the steps of heating a steel billet of hot work die steel, rough rolling, first heat-preserving cooling, middle rolling, second heat-preserving cooling, three-roller reducing sizing finish rolling, third heat-preserving cooling, sawing, collecting, bundling, pit-entering slow cooling and pit-leaving to obtain the hot work die steel bar;
the total alloy element content of the hot work die steel is more than 8 percent by weight, and the diameter specification of the finished product is phi 30-phi 70;
The total pass of the rough rolling and the middle rolling is 12-16 times;
And the three-roller reducing sizing finish rolling is carried out, the diameter specification of the reducing sizing incoming material is phi 40-phi 75, and the finish rolling passes are 4-5 times.
According to the rolling method, the heating rolling process of three-roller reducing sizing finish rolling of the medium-small-specification high alloy bar is designed, the forming pass of different finished product specification ranges and the reducing sizing incoming material specification are designed, the rolling dimensional precision of the high alloy hot working die steel bar is improved, and free rolling of any specification from phi 30 to phi 70 is realized. Meanwhile, the three-roller reducing sizing mill finish rolling finished product replaces the conventional two-roller mill finished product, the step of turning finish machining after two-roller rolling is omitted, the machining cost is reduced, and the machining flow is shortened. As an alternative implementation mode of the invention, the finish rolling passes are 4 times or 5 times, 3 passes can be used for rolling in the specification with smaller reduction, but 3 passes are unstable in rolling, the problems of rolling surface and size are easy to occur, and for high alloy varieties, the variety has larger deformation resistance and is more easy to cause the problems. The 4-pass technology is mature and stable in rolling, the 5-pass technology is not mature at present, and the hole pattern design is carried out according to 4-pass preference. As an alternative embodiment of the invention, the hot work die steel is 4Cr5MoSiV1. The main chemical components (mass percent) of the 4Cr5MoSiV1 are ：C：0.32～0.45％、Si：0.80～1.20％、Mn：0.2～0.5％、P：≤0.025％、S：≤0.025％、Cr：4.75～5.50％、Ni：≤0.2％、Cu≤0.2％、V：0.80～1.20％、Mo:1.10～1.75％,, and the balance is matrix Fe and unavoidable impurities. The total alloy element content of 4Cr5MoSiV1 is higher (more than 8%wt), and the alloy has the characteristics of high hardness, high deformation resistance, easiness in cracking and the like, and is a typical difficult-to-process material. The small-size 4Cr5MoSiV1 bar is prepared by adopting the rolling method, the defects of unstable tolerance, lugs, folding and the like during two-roll rolling can be overcome, compared with the 3 groups of tolerance levels of national standard GB/T702-2017 which can only be met by the dimensional tolerance under the condition of better two-roll rolling, the dimensional precision is greatly improved, the tolerance size of the 4Cr5MoSiV1 bar with the specification of phi 30-phi 70 after rolling meets 0 to +0.5mm, the out-of-roundness is less than or equal to 0.35mm, the defects of surface folding, lugs, stress cracking and the like are overcome, and the flaw detection quality meets the A-level requirements of GB/T4162-2022 standard.
Further, the log diameter gauge may typically, but not limitatively, be selected from Φ31, Φ33, Φ36, Φ38, Φ40, Φ41, Φ43, Φ46, Φ48, Φ50, Φ52, Φ55, Φ57, Φ60, Φ62, Φ64, Φ66, Φ68, Φ70. The total number of passes of the rough rolling and the intermediate rolling is typically, but not limited to, 13, 14, and 15. The diameter specification of the reducing sizing incoming material is fixed, so that the same group distance free roll changing can be conveniently realized, and the roll changing time is shortened.
Further, when the diameter specifications of the finished product are phi 30-phi 36 and phi 36-phi 41 respectively, the total pass of rough rolling and middle rolling is 16 times, and the diameter specifications of the reduced sizing incoming material are phi 40 and phi 46 respectively; when the diameter specifications of the finished products are phi 41-phi 48 and phi 48-phi 57 respectively, the total pass of rough rolling and middle rolling is 14 times, and the diameter specifications of the reduced sizing incoming materials are phi 52 and phi 61 respectively; when the diameter specifications of the finished products are phi 57-phi 64 and phi 64-phi 70 respectively, the total pass of rough rolling and middle rolling is 12 times, and the diameter specifications of the reduced sizing incoming materials are phi 68 and phi 75 respectively. Still further, the rough rolling passes are 6 passes.
As an alternative embodiment of the rolling process of the invention, the heated preheating section temperature: 550-650 ℃ (such as 555 ℃, 560 ℃, 570 ℃, 580 ℃, 590 ℃, 600 ℃, 610 ℃, 620 ℃, 630 ℃, 640 ℃, 645 ℃) and soaking section temperature: 1170-1230 ℃ (such as 1175 ℃, 1180 ℃, 1185 ℃, 1190 ℃, 1195 ℃, 1200 ℃, 1205 ℃, 1210 ℃, 1215 ℃, 1220 ℃, 1225 ℃) and soaking and heat preserving time of 60-120 min (such as 70min, 80min, 90min, 100min, 110 min).
As an alternative embodiment of the rolling method of the present invention, the initial rolling temperature of the rough rolling: 1070-1130 deg.C (1075 deg.C, 1080 deg.C, 1085 deg.C, 1090 deg.C, 1095 deg.C, 1100 deg.C, 1105 deg.C, 1110 deg.C, 1115 deg.C, 1120 deg.C, 1125 deg.C).
As an alternative implementation mode of the rolling method, the rough rolling is preceded by adopting high-pressure air to perform descaling, so that the high-pressure water is replaced for descaling, and the heat loss in the descaling process is reduced.
As an alternative embodiment of the rolling method of the present invention, the finishing temperature of the three-roll reducing finishing rolling: more than or equal to 920 ℃ (such as 925 ℃, 930 ℃, 935 ℃, 940 ℃, 945 ℃ and 950 ℃).
As an alternative embodiment of the rolling method of the invention, the first heat-preserving cooling and the second heat-preserving cooling are both carried out on a roller bed provided with a heat-preserving cover; the third heat preservation and cooling are carried out on a cooling bed with a heat preservation cover. Further, the temperature of the cooling bed on the steel billet is as follows: more than or equal to 880 ℃ (such as 885 ℃, 890 ℃, 895 ℃, 900 ℃, 905 ℃, 910 ℃, 915 ℃, 920 ℃,925 ℃) and the temperature of the cooling bed heat preservation cover: 550-650 ℃ (such as 555 ℃, 560 ℃, 570 ℃, 580 ℃, 590 ℃, 600 ℃, 610 ℃, 620 ℃, 630 ℃, 640 ℃, 645 ℃). According to the rolling method, the rolled alloy bar is subjected to heat preservation and cooling, so that rolling difficulty or stress cracking caused by too high cooling speed is avoided.
As an alternative embodiment of the rolling method of the present invention, the temperature of pit entry slow cooling: more than or equal to 350 ℃ (such as 355 ℃, 360 ℃, 365 ℃, 370 ℃, 375 ℃, 380 ℃, 385 ℃, 390 ℃, 395 ℃); the pit outlet temperature is as follows: less than or equal to 100 ℃ (such as 95 ℃, 90 ℃, 85 ℃,80 ℃, 75 ℃, 70 ℃, 65 ℃ and 60 ℃). The rolling method of the invention is characterized by pit entry and slow cooling, and avoids metallurgical defects such as white spots and the like.
In the research and development process, the invention discovers that 4Cr5MoSiV1 belongs to air quenched martensitic high alloy steel, and the alloy steel has stronger crack sensitivity and higher high-temperature deformation resistance. The 4Cr5MoSiV1 crack has higher sensitivity, the heating preheating temperature and the cooling temperature after rolling are required to be controlled, and the heating is not suitable to be too fast at low temperature, so that the stress crack is avoided; the low-melting-point region of the grain boundary is easy to burn when the heating temperature of the 4Cr5MoSiV1 is more than 1240 ℃, so that the soaking and heat preserving temperature is required to be slightly lower than 1240 ℃; the deformation resistance of the 4Cr5MoSiV1 generally tends to be improved along with the reduction of the temperature, and the plasticity of the steel is reduced rapidly when the temperature is lower than 880 ℃, so that the rolling temperature is selected to be as high as possible, and the rolling mill is convenient to bite and roll smoothly; the 4Cr5MoSiV1 is easy to generate metallurgical defects such as white spots, and the like, so that the alloy is suitable for slow cooling at about 250 ℃, is convenient for the diffusion of H element, and avoids the white spot defects generated by aggregation of the H element.
The present invention will be described in further detail with reference to specific examples.
Examples 1 to 9
A rolling method for improving the dimensional accuracy of a steel bar of a high alloy hot working die is designed and controlled, and a rolling process for heating, rolling temperature and forming pass is as follows:
1. The process flow comprises the following steps:
Billet heating in a step furnace, rough rolling (high-pressure air descaling before rough rolling), first heat preservation cooling, middle rolling, second heat preservation cooling, three-roll reducing sizing finish rolling, third heat preservation cooling, sawing, collecting, bundling, pit entering and slow cooling, pit discharging;
2. Designing forming passes with different forming material specification ranges and reducing sizing incoming material specifications:
| Specification range of finished product | Blank specification | Rough rolling and intermediate rolling pass | Reducing sizing incoming material specification | Finish pass |
| Φ30-Φ36 | 240 X 240 square | 16 | Φ40 | 4 |
| Φ36-Φ41 | 240 X 240 square | 16 | Φ46 | 4 |
| Φ41-Φ48 | 240 X 240 square | 14 | Φ52 | 4 |
| Φ48-Φ57 | 240 X 240 square | 14 | Φ61 | 4 |
| Φ57-Φ64 | 240 X 240 square | 12 | Φ68 | 4 |
| Φ64-Φ70 | 240 X 240 square | 12 | Φ75 | 4 |
Wherein, rough rolling is 6 times;
3. preheating section temperature: 600+/-50 ℃ and soaking section temperature: soaking and preserving the heat for 60-120 min at 1200+/-30 ℃.
4. Start rolling temperature: 1100.+ -. 30 ℃.
5. Finishing temperature: and is more than or equal to 920 ℃.
6. Upper cooling bed temperature: not less than 880 ℃.
7. Temperature of heat preservation cover of cooling bed: 600+ -50 DEG C
8. Pit entering temperature: not less than 350 ℃.
9. Pit outlet temperature: the temperature is less than or equal to 100 ℃.
10. And high-pressure air is adopted to remove scales before rough rolling, so that the high-pressure water is replaced to remove scales, and the heat loss in the descaling process is reduced.
11. The roller tables with the heat preservation covers are arranged after rough rolling and medium rolling, the cooling bed with the heat preservation covers is arranged after finish rolling, heat preservation and cooling are carried out on the rolled alloy bar, and rolling difficulty or stress cracking caused by too fast cooling speed is avoided.
12. After being collected and bundled, the steel is put into a pit for slow cooling, so that metallurgical defects such as white spots and the like are avoided.
9 Batches of high-alloy bars (4 Cr5MoSiV1 bars) with the specification of 30-70 mm are produced according to a designed rolling process, and are respectively in examples 1-9.
Comparative example 1
The only difference from example 1 is that the soaking section temperature was higher at 1245 ℃ when comparative example 1 was heated.
Comparative example 2
The only difference from example 1 is that the upper cooling bed temperature was lower at 875 ℃ when the cooling bed of comparative example 2 was cooled.
Comparative example 3
The difference from example 1 was only that the finish rolling temperature was 915℃lower in the finish rolling of comparative example 3.
Performance testing
The steels obtained in the examples and comparative examples were tested, the tolerance size test was performed according to GB/T702-2017, the ultrasonic flaw detection was performed according to GB/T4162-2022 standard A-class, and the test results are shown in Table 1:
TABLE 1 test results after hot working die Steel grade 4Cr5MoSiV1 examples and comparative examples were rolled
The 4Cr5MoSiV1 high alloy bar rolled by adopting the process disclosed by the invention has the specification range phi 30-phi 70, the roll replacement is not needed in the same group of distance specifications, free rolling can be realized by any specification to meet the individual requirements of customers on the steel size, and the process tool is simple to prepare and high in production efficiency. The tolerance size after rolling is +0.1- +0.4mm, the out-of-roundness is less than or equal to 0.25mm, the defects of surface folding, lugs, stress cracking and the like are avoided, the flaw detection quality meets the GB/T4162-2022 standard A-level requirement, and the rolling size precision is far higher than that of the conventional two-roll rolling technology. The heating temperature of the comparative example 1 is higher, the overburning phenomenon is generated, and the ultrasonic flaw detection qualification rate is obviously reduced; comparative example 2, the lower temperature of the upper cooling bed can lead to the reduction of the heat preservation effect of the cooling bed, the quickened cooling speed of steel, the increased risk of core stress cracking and the reduction of the core flaw detection qualification rate. Comparative example 3, in which the finishing temperature is low, the increase in the deformation resistance of the steel product leads to an obvious increase in the dimensional dispersion; meanwhile, the plasticity is reduced rapidly, the core stress cracking risk is increased, and the core flaw detection qualification rate is reduced more.
The foregoing description of the preferred embodiments of the invention is not intended to limit the invention, but rather to enable any modification, equivalent replacement, improvement or the like to be made within the spirit and principles of the invention, and is within the scope of the appended claims.
Claims (10)
1. A rolling method of a high alloy hot work die steel bar is characterized in that a billet of hot work die steel is sequentially heated, rough rolled, first heat-preserving cooled, middle rolled, second heat-preserving cooled, three-roll reducing sizing finish rolled, third heat-preserving cooled, saw cut, collected, bundled, slowly cooled in a pit and discharged from the pit to obtain the hot work die steel bar;
the total alloy element content of the hot work die steel is more than 8 percent by weight, and the diameter specification of the finished product is phi 30-phi 70;
The total pass of the rough rolling and the middle rolling is 12-16 times;
And the three-roller reducing sizing finish rolling is carried out, the diameter specification of the reducing sizing incoming material is phi 40-phi 75, and the finish rolling passes are 4-5 times.
2. The rolling method according to claim 1, wherein the hot work die steel has a grade of 4Cr5MoSiV1;
and/or when the diameter specification of the finished product is phi 30-phi 36 and phi 36-phi 41 respectively, the total pass of rough rolling and middle rolling is 16 times, and the diameter specification of the reduced sizing incoming material is phi 40 and phi 46 respectively;
And/or when the diameter specifications of the finished product are phi 41-phi 48 and phi 48-phi 57 respectively, the total pass of rough rolling and middle rolling is 14 times, and the diameter specifications of the reduced sizing incoming material are phi 52 and phi 61 respectively;
And/or when the diameter specifications of the finished product are phi 57-phi 64 and phi 64-phi 70 respectively, the total pass of rough rolling and middle rolling is 12 times, and the diameter specifications of the reduced sizing incoming material are phi 68 and phi 75 respectively;
and/or, the rough rolling passes are 6 passes;
And/or, the finish rolling passes are 4 passes.
3. The rolling process of claim 1, wherein the heated preheat section temperature: 550-650 ℃, soaking section temperature: 1170-1230 ℃, soaking and preserving heat for 60-120 min.
4. The rolling method according to claim 1, wherein the initial rolling temperature of the rough rolling: 1070-1130 ℃;
And/or, the rough rolling is preceded by adopting high-pressure air to remove scales.
5. The rolling method according to claim 1, characterized in that the finishing temperature of the three-roll reducing finishing rolling: and is more than or equal to 920 ℃.
6. The rolling method according to claim 1, wherein the first and second heat-preserving cooling are performed on a roller table provided with a heat-preserving cover; the third heat preservation and cooling are carried out on a cooling bed with a heat preservation cover.
7. The rolling method of claim 6 wherein the cold bed temperature on the billet: the temperature of the cooling bed heat preservation cover is not less than 880 ℃: 550-650 ℃.
8. The rolling method according to claim 1, wherein the temperature of pit entry slow cooling: not less than 350 ℃; the pit outlet temperature is as follows: the temperature is less than or equal to 100 ℃.
9. A high alloy hot work die steel bar, characterized in that it is obtained by the rolling method according to any one of claims 1-8.
10. The high alloy hot work die steel bar according to claim 9, wherein the high alloy hot work die steel bar is a 4Cr5MoSiV1 bar, preferably the 4Cr5MoSiV1 bar has a diameter specification of Φ30- Φ70, a detection tolerance size of 0 to +0.5mm according to GB/T702-2017, and a non-circularity of 0.35mm or less; the ultrasonic flaw detection quality meets the A-level requirement of GB/T4162-2022 standard.
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